Halakhah zu Wajikra 16:33

And this commandment is practiced with non-sacred animals, but not with those consecrated; by Israelite males and females, but not by priests - since it is written about them, "the statute of the priests from the people," which implies that it is not from the priests. And [this is the case] also because the priests are not called, "people"; and as it is written (Leviticus 16:33), "he shall atone for the priests, and for all the people of the congregation." And the Levites have a special law in this matter; as the priests do not take the gifts from them - since the Rabbis were in doubt if they are called "people," or not. And hence they can not take from them by force of a doubt; but if they took [the gifts], they do not return [them].